Method for producing an electrical contact

ABSTRACT

A method for producing an electrical contact is disclosed. In an embodiment the method includes providing a piezoelectric component that includes an electromechanical transducer having two first electrodes and a second electrode arranged between the two first electrodes and spaced from the two first electrodes by a piezoelectric material, the transducer further including a first main side, a second main side opposite from the first main side and a first longitudinal side, and forming a contiguous metallization layer onto a first partial region of the first main side and onto a second partial region along the first longitudinal side, so that the second partial region along the first longitudinal side is at a distance from a side edge facing the second main side and the metallization layer in the second partial region of the first longitudinal side contacts the two first electrodes in an electrically conducting manner.

This is a divisional application of U.S. application Ser. No.12/970,590, which was filed on Dec. 16, 2010, which is a continuation ofco-pending International Application No. PCT/EP2009/057482, filed Jun.16, 2009, which designated the United States and was not published inEnglish, and which claims priority to German Application No. 10 2008 029185.4, filed Jun. 19, 2008, all of which applications are incorporatedherein by reference.

TECHNICAL FIELD

The invention relates to a piezoelectric component and to a method forproducing a contact, in particular, on a piezoelectric component.

BACKGROUND

Piezoelectric components are known, for example, from the U.S. Pat. No.6,346,764 B1.

Piezoelectric components of this kind are used in many applications. Onetypical application is that of actuators, in which a control voltage isused to induce a piezoelectric component to perform vibrations, forexample, bending or stretching vibrations. A natural resonant frequencyof the piezoelectric component is obtained from the geometric dimensionsof the component in conjunction with its elastic properties. Thesecharacterize a response of the piezoelectric component to an electricalinducement supplied to the component.

In a typical application, one or more piezoelectric components are usedas an actuator, in order to create a piezoelectric motor. By electricalinducement, that is to say the formation of an alternating electricfield, the piezoelectric component is induced to perform vibrations, andtransmits them to an element that is coupled to it. As a result, forexample, a thread makes a motor undergo axial rotation and in this waymakes it move.

The elements that are mechanically connected to the piezoelectriccomponent to form an actuator are often electrically conductive. Thismakes particular demands on the mechanical fastening of the component.For instance, the mounting side of the component should be electricallyinsulated from the electrical contacting of the electrodes within thepiezoelectric component in order to avoid a short-circuit betweenvarious piezoelectric components on the construction that is to becreated. On the other hand, it should be possible for the individualelectrodes within the piezoelectric component to be contacted withoutgreat resistance, in order to minimize power losses.

SUMMARY

In one aspect, the present invention provides a piezoelectric componentin which sufficiently good contacting is ensured. In another aspect, amethod for producing an electrical contact, in particular on apiezoelectric component, is disclosed.

Until now, contacting of a piezoelectric component has been performed bywhat is known as an immersion process. In this, the component is wettedwith a metal layer and the contact is formed in this way. However, themethod involves wetting or metalizing all the sides of the component. Ifsome regions, for example, side surfaces, of the piezoelectriccomponent, are not to be metalized, complex measures are necessary toprevent unwanted metallization.

The inventors now propose a piezoelectric component which comprises anelectromechanical transducer. This has at least two first electrodes andat least one second electrode, which is arranged between the at leasttwo first electrodes and is kept at a distance from them by apiezoelectric material. Furthermore, the transducer comprises a firstmain side, a second main side, opposite from the first main side, and afirst longitudinal side. The piezoelectric component is distinguishedfurthermore by a contiguous metallization layer on a first partialregion of the first main side and on a partial region of thelongitudinal side that is adjacent to the first partial region of thefirst main side. Here, the partial region of the longitudinal side is ata sufficiently insulating distance from a side edge facing the secondmain side. Furthermore, this partial region electrically contacts the atleast two electrodes.

According to embodiments of the invention, a free border in which thereis no metallization, and which consequently permits insulation of thesecond main side, is formed so as to run along the longitudinal side.The metallization layer applied to the first main side within the firstpartial region and the partial region of the longitudinal side that isin electrical connection therewith permits the formation of a contactover a large area on the first main side, which contacts the at leasttwo first electrodes in an electrically conducting manner by way of themetallization layer applied to the partial region of the longitudinalside.

The contiguous metallization layer is in this case advantageouslysputtered on. The sputtering process may be performed in such a way thatthe metallization layer is advantageously applied substantiallysimultaneously both on the first partial region of the first main sideand on the partial region of the longitudinal side that is adjacent tothe first partial region.

Similarly, the metallization layer may also extend to a partial regionon the second longitudinal side, which is arranged opposite from thefirst longitudinal side. Consequently, the metallization layer canextend to partial regions that are arranged on both sides along thelongitudinal side of the piezoelectric component and electricallycontact the at least two first electrodes within the piezoelectriccomponent. In both cases, the partial regions along the longitudinalsides are at a distance from the side edge facing the second main side.In other words, the metallization layer along the longitudinal side doesnot extend completely over the entire width of the longitudinal side butonly over a partial region. This partial region is facing the first mainside. A border, for example, with a thickness in the range from 2 μm to14 μm, between the partial region on the longitudinal side and the sideedge between the longitudinal side and the second main side, remainsfree of metallization. This ensures that, when the piezoelectriccomponent is mounted with the second main side on a body, the latterdoes not lead to an electrical short circuit with the metallizationlayers located on the longitudinal sides.

In addition, the metallization layer may also extend to a partial regionalong a third longitudinal side. For example, the third longitudinalside may form the transverse side of the piezoelectric component or ofthe electromechanical transducer.

To prevent a short-circuit of the at least two electrodes, in arefinement it is envisaged to form them in a partial region of thetransducer outside the partial region of the first longitudinal side ata distance from a surface of the first longitudinal side. As a result,the electrodes have smaller dimensions in a partial region of thetransducer outside the metallization layer and, in particular, do notreach as far as the surface of the longitudinal side.

In this way it is possible to form a second contiguous metallizationlayer on a second partial region of the first main side of thetransducer and on a partial region of the longitudinal side adjacent tothe second partial region. The second metallization layer on the secondpartial region is correspondingly kept at a distance from themetallization layer on the first partial region. In the same way, thepartial regions arranged on the longitudinal side are kept at a distancefrom one another. Moreover, the partial region of the longitudinal sidewith the metallization layer is also electrically insulated from theside edge facing the second main side, so that a possible short-circuitwith a mounting element arranged on the second main side is avoided.

The second metallization layer on the first main side and thelongitudinal side serves the purpose of contacting the at least onesecond electrode in an electrically conducting manner. At the same time,the second metallization layer is electrically insulated from the atleast two first electrodes. This may be performed, for example, by theat least two first electrodes in the partial region of the longitudinalside being adjacent to the second partial region within the transducerand not reaching the surface on the longitudinal side. The same alsoapplies correspondingly to the second electrode in the first partialregion and the partial regions of the longitudinal side adjacentthereto.

In this way, two metallization layers that are spaced apart andelectrically insulated from one another, with the aid of which the atleast two first and at least one second electrode(s) are contacted in anelectrically conducting manner, can be formed on the first main side. Ina refinement, the metallization layer on the piezoelectric component hasa thickness of from 0.3 μm to 5 μm, and in particular a thickness offrom 0.5 μm to 2 μm.

In a refinement, the piezoelectric component has a step on the first orsecond main side. This step may serve the purpose, for example, ofpermitting mechanical coupling to a mounting element to which amechanical vibration brought about by the piezoelectric component is tobe transmitted. Moreover, further mechanical refinements that areelectrically insulated on account of the insulation and the distancefrom the metallization layer along the longitudinal side or first mainside may be carried out on the second main side.

In a refinement, the step on the second main side is arranged in aregion which lies outside a projection of the first or second partialregion on the first main side.

The metallization layer is sputtered on in the partial region along thelongitudinal side and the first main side. This allows the metallizationlayer to be applied substantially simultaneously on the partial regionsof the first and/or second main side or of the longitudinal sides.Moreover, by a suitable offset of the piezoelectric component inrelation to the sputtering direction it can be ensured that anelectrical resistance of the metallization layer along the side edgebetween the first main side and the longitudinal side is low and has noeffects on the operation and electrical contacting of the electrodes.

In a method for producing contacting areas, in a first step, apiezoelectric component which comprises an electromechanical transduceris provided. This transducer includes at least two first electrodes,between which a second electrode is arranged and is kept at a distancefrom the first electrodes by a piezoelectric material. Theelectromechanical transducer consequently comprises a series ofalternately arranged electrodes which are enclosed by a piezoelectricmaterial. Furthermore, the transducer has a first main side, a secondmain side, opposite from the first main side, and a first longitudinalside.

According to embodiments of the invention, sputtering on of a contiguousmetallization layer for the contacting of the electrodes is envisaged.The metallization layer is sputtered on, on a partial region of thefirst main side and on a partial region of the longitudinal sideadjacent to the partial region of the first main side.

This is performed in such a way that the metallization layer in thepartial region along the longitudinal side does not run completely overthe width of the longitudinal side, but instead the metallization layeris at a distance from a side edge facing the second main side. In otherwords, along the longitudinal side a “free border,” which is free from ametallization layer, is formed between the partial region and the sideedge facing the second main side. The sputtering material therefore doesnot get into the region of the free border during the production method.

The metallization layer on the partial region along the firstlongitudinal side is in electrically conducting contact with themetallization layer on the partial region of the first main side and,moreover, contacts the at least two first electrodes of theelectromechanical transducer in an electrically conducting manner.

In a further embodiment, a second contiguous metallization layer issputtered on, on a second partial region of the first main side that isat a distance from the first partial region of the first main side.Consequently, the first partial region and the second partial region areelectrically insulated from one another.

A metallization layer is moreover also sputtered on, on partial regionsof the longitudinal side adjacent to the second partial region of thefirst main side, so that the metallization layer along the longitudinalside and that on the partial region of the first main side are inconnection with one another in an electrically conducting manner. Themetallization layer on the partial region of the first longitudinal sideadjacent to the second partial region contacts the at least one secondelectrode. Moreover, it does not extend over the complete width of thelongitudinal side, but instead a border that is not covered by ametallization layer remains between the partial region along thelongitudinal side and the side edge facing the second main side.

BRIEF DESCRIPTION OF THE DRAWINGS

For the remainder, the invention is explained in more detail on thebasis of various embodiments with reference to the drawings, in which:

FIG. 1A shows a cross-sectional representation of a piezoelectriccomponent with sputtered-on metallization according to a firstembodiment;

FIG. 1B shows a plan view of the piezoelectric component as shown inFIG. 1A;

FIG. 2 shows a piezoelectric component according to one embodiment afterthe sputtering on of the metallization layer in a first perspectiveview;

FIG. 3 shows the piezoelectric component as shown in FIG. 2 in a secondperspective view;

FIG. 4 shows a piezoelectric component according to a first embodimentbefore the sputtering on of the metallization layer; and

FIG. 5 shows a device for carrying out a sputtering process forpiezoelectric components according to the proposed method.

The embodiments that are presented and explained in the figures thatfollow are not drawn with their individual elements to scale. Inparticular, individual elements may be shown over-large or over-smallfor more precise illustration. Individual aspects that are only referredto in certain embodiments, for example, layer thicknesses, distances ormaterials, can be readily transferred to the other embodiments.Components that are the same in terms of effect and function bear thesame designations.

The following list of reference symbols may be used in conjunction withthe drawings:

-   -   1 electromechanical transducer    -   10 a piezoelectric material    -   10 first main side    -   11 second main side    -   12, 13 longitudinal side    -   14 transverse side    -   21, 22 electrodes    -   30, 30′ metallization layer    -   31, 31′ first partial region    -   40, 40′, 42 second partial region    -   51, 52, 53 side edge    -   D, E distance

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1A shows a cross-sectional representation of a piezoelectriccomponent with a sputtered-on metallization layer for the contacting ofindividual electrodes within the electromechanical transducer of thecomponent.

The electromechanical transducer 1 comprises a multiplicity of firstelectrodes 21 and second electrodes 22, arranged one above the other.These electrodes are kept at a distance by a piezoelectric material 10 awhile forming a sequence of layers arranged such that they alternate oneabove the other. The respectively outer electrodes are also surroundedby a further layer, so that the electrodes are completely enclosed inthe electromechanical transducer 1. For the contacting of the individualelectrodes 21 and 22, metallization layers are sputtered on, on the sidewalls and the first main side 10. The metallization layer 30 is in thiscase arranged on the side surface in such a way that it electricallycontacts the individual first electrodes 21. For this purpose, in thepartial region of the longitudinal side of the piezoelectric componentin which the metallization layer 30 is located, the first electrodes 21are led to the surface of the longitudinal side. This structure isrepresented in FIG. 1B, which shows a plan view of one of the electrodes21.

In the partial regions 40 and 41 of the longitudinal sides 12 and 13 ofthe piezoelectric component, the metallization layer 30 is sputtered on.In these partial regions on the longitudinal side, the electrode 21 hasa width which corresponds substantially to the width of the transducer1. In other words, in the partial regions 40 and 41, the electrodes 21are led to the surface on the longitudinal side of the component and areconsequently in conducting connection with the metallization layer inthe partial regions 40 and 41.

Outside the partial regions 40 and 41, the electrodes 21 have a slightlysmaller width, so that a slight distance E remains between the surfaceon the longitudinal side of the component and the electrode. Theelectrodes 21 are consequently surrounded by an insulating material.This ensures that the electrodes 21 do not reach the surface of thelongitudinal side 12 or 13 of the component and so possibly cause ashort circuit. In particular, the electrode 21 in partial regions 40′and 41′ of the longitudinal sides 12 and 13 is electrically insulatedfrom the metallization layer 30′ there.

The electrodes 22 in the partial regions 40′ and 41′ are in turnconnected in an electrically conducting manner to the metallizationlayer 30′ applied there. Their form corresponds substantially to theelectrodes 21, only they are swapped over and their wide side is on thesurface on the longitudinal side in the partial regions 40′ and 41′,where it contacts the metallization layer.

In this way, the metallization layer 30 on the first main side of thepiezoelectric component, represented by the dashed line, contacts theelectrodes 21. In a corresponding way, the metallization layer 30′ onthe first main side of the component contacts the electrodes 22 withinthe electromechanical transducer by way of the metallization layer onthe partial regions 40′ and 41′ of the longitudinal sides 12 and 13. Theregion 61 on the first main side of the piezoelectric component is freeand not covered by a sputtered-on metallization layer.

FIG. 2 shows a perspective representation of the piezoelectric componenton the basis of the proposed principle with the sputtered-onmetallization layers for contacting the electrodes within theelectromechanical transducer 1. The piezoelectric component comprisesthe electromechanical transducer 1 with a first main side 10 and asecond main side 11, which can be seen here. In the present exemplaryembodiment, the second main side 11 is intended to be free from ametallization layer, since it serves as a side for mounting thepiezoelectric component. In order to avoid a short circuit, it istherefore necessary to design the contacting and the electrodes withinthe electromechanical transducer 1 in such a way as to avoid anelectrically conducting connection with respect to the second main side11, and consequently a short circuit.

In this exemplary embodiment, a metallization layer is applied along thelongitudinal side 12 in the partial regions 40 and 40′. Thismetallization layer contacts electrodes within the electromechanicaltransducer. Moreover, the partial regions 40 and 40′ with themetallization layer sputtered on them are kept at a distance from theside edge 51 by way of the distance D. In this way, a free border isformed between the partial regions 40 and 40′ and the side edge 51. Theside edge 51 accordingly “connects” the longitudinal side 12 to thesecond main side 13.

Defined on a transverse side 14 of the electromechanical transducer 1 isa further partial region 42, in which the metallization layer islikewise sputtered on. This layer is also kept away from the side edge53 by way of a free border with the distance D. The free border with thedistance D, which lies, for example, in the range from 2 to 14 μm,ensures sufficient insulation of the metallization layers on the partialregions 40, 40′ and 42 from the second main side 11.

Furthermore, the electromechanical transducer 1 is configured in such away that, in the region of the free border, that is to say in the regionbetween the second main side with the side edges 51, 52 and 53 and therespective partial regions 40, 40′ and 42, no further electrodes arearranged within the transducer.

FIG. 3 shows the piezoelectric component according to FIG. 2 from asecond perspective view. The partial regions 40, 40′ and 42 arranged onthe longitudinal sides are connected in an electrically conductingmanner to the metallization layer on the partial regions 31 and 31′ ofthe first main side 10 by way of the side edge 55 on the longitudinalside or the transverse edge 56. Moreover, contacting areas 80 have beenapplied to the metallization layer 30, 30′ of the two partial regions 31and 31′. With the aid of the contacting areas 80, control signals can besupplied to the electrodes within the electromechanical transducer 1.The connection to the inner electrodes consequently takes place on thelongitudinal side of the component by way of an electrically conductingconnection to contacts on the upper side 10 of the electromechanicaltransducer 1. The metallization layer 30, 30′ over the side edges 55, 56and 56′ is in this case configured in such a way that it does not havean increased electrical resistance.

FIG. 4 shows a further embodiment of a piezoelectric component in aperspective representation before the sputtering on of the metallizationlayer. In the case of this embodiment, an additional step 70 has beenintroduced on the second main side 11, the underside. This step isrequired by the structural design and serves for the later fastening toa motor that is operated by the piezoelectric component and theelectromechanical transducer 1. In the embodiment, the electromechanicaltransducer comprises two partial regions 1 a and 1 b, which are kept ata distance from one another by a field-free and electrode-free region61. In the partial region 61, the step 70 has likewise been introducedon the second main side. In addition, the component has a bordersurrounding the electromechanical transducer on three sides, so that onthe second main side 11 there is an additional step 71 at a distancefrom the side edge 53.

The partial regions 1 a and 1 b respectively comprise a multiplicity ofelectrodes 21 and 22, arranged such that they alternate one above theother and are kept apart by piezoelectric material. In the refinement itis provided that the electrodes 21 are respectively led to the surfaceof the longitudinal side 13 of the component. By contrast with this, theelectrodes 22 are arranged such that they are insulated from the surfaceof the electromechanical transducer and “floatin″” within theelectromechanical transducer 1. An inducement of the electromechanicaltransducer 1 to produce a vibration consequently takes place bysupplying an activating potential to the electrodes 21. As a result, theelectromechanical transducer 1 performs vibrations, and in particularbending vibrations.

For the contacting of the electrodes 21, the electromechanicaltransducer 1 is then introduced into a rack, the first main side 10being arranged at an angle of about 25° to the sputtering direction. Arack of this kind is represented in FIG. 5. Since the step is not to beprovided with a metallization, the electromechanical transducer as shownin FIG. 4 is fitted in the rack in such a way that the first main side10 is facing upward in the sputtering direction.

Subsequently, the metallization layer is sputtered with a thickness inthe range from 0.5 μm to 2 μm onto the partial regions 1 a and 1 b ofthe first main side 10. On account of the step 70 introduced into thecomponent surface, the component is fitted in a rack in such a way thatthe first main side 10 is facing upward, to avoid short-circuits in themounted state during the sputtering. An overlap on the second main side11, the mounting side of the component, that possibly occurs during thesputtering can in this way be neutralized. The metallization over thelongitudinal edge is in this case performed by way of the sputteringrack represented in FIG. 5.

What is claimed is:
 1. A method for producing an electrical contact, themethod comprising: providing a piezoelectric component that comprises anelectromechanical transducer comprising two first electrodes and asecond electrode arranged between the two first electrodes and spacedfrom the two first electrodes by a piezoelectric material, thetransducer further comprising a first main side, a second main sideopposite from the first main side and a first longitudinal side; andforming a contiguous metallization layer onto a first partial region ofthe first main side and continuously onto a second partial region alongthe first longitudinal side so that the second partial region along thefirst longitudinal side is at a distance from a side edge facing thesecond main side and the contiguous metallization layer in the secondpartial region of the first longitudinal side contacts the two firstelectrodes in an electrically conducting manner, wherein the contiguousmetallization layer is also continuously formed over a fourth partialregion of a second longitudinal side, opposite from the firstlongitudinal side so that the fourth partial region of the secondlongitudinal side is at a distance from the side edge facing the secondmain side and the contiguous metallization layer contacts the two firstelectrodes.
 2. The method as claimed in claim 1, wherein the distancelies in a range between 2 μm and 14 μm.
 3. The method as claimed inclaim 1, wherein the contiguous metallization layer extends over a sideedge between the first partial region of the first main side and thesecond partial region of the first longitudinal side.
 4. The method asclaimed in claim 1, wherein a contact on the contiguous metallizationlayer is applied to the first partial region of the first main side. 5.The method as claimed in claim 1, wherein the transducer furthercomprises a transverse side adjacent the first and second main sides andadjacent the first longitudinal side, the transverse side comprising athird partial region that is adjacent to the first partial region of thefirst main side, wherein the contiguous metallization layer is arrangedon the third partial region and contacts the two first electrodes in anelectrically conducting manner, the third partial region of thetransverse side spaced from a side edge facing the second main side. 6.The method as claimed in claim 1, wherein the two first electrodes in apartial region of the transducer outside the second partial region ofthe first longitudinal side are at a distance from a surface of thefirst longitudinal side.
 7. The method as claimed in claim 6, wherein asecond longitudinal side which is arranged opposite from the firstlongitudinal side, comprises a fourth partial region that is adjacent tothe first partial region of the first main side, wherein the contiguousmetallization layer is arranged on the fourth partial region andcontacts the two first electrodes in an electrically conducting manner,the fourth partial regional of the second longitudinal side spaced fromthe side edge facing the second main side.
 8. The method as claimed inclaim 1, further comprising forming a second contiguous metallizationlayer on a fifth partial region of the first main side of the transducerthat is spaced from the first partial region and on a sixth partialregion of the first longitudinal side that is adjacent to the secondpartial region, the first partial region being at a distance from theside edge facing the second main side and the second contiguousmetallization layer contacting the second electrode in an electricallyconducting manner.
 9. The method as claimed in claim 1, wherein formingthe contiguous metallization layer comprises sputtering the contiguousmetallization layer.
 10. The method as claimed in claim 1, wherein thecontiguous metallization layer is formed to a thickness of from 0.3 μmto 5 μm.
 11. The method as claimed in claim 1, wherein the contiguousmetallization layer is formed to a thickness of from 0.5 μm to 2 μm. 12.The method as claimed in claim 1, wherein the component has a step onthe first or second main side.
 13. The method as claimed in claim 12,wherein the step is arranged in a partial region of the transduceroutside the first partial region.
 14. The method as claimed in claim 1,wherein the second main side is free from a metallization layer.
 15. Themethod as claimed in claim 1, wherein the two first electrodes and thesecond electrode are arranged substantially in parallel to the firstmain side.